Neurourology and Urodynamics 33:1251–1258 (2014) The Fatty Acid Amide Hydrolase Inhibitor Oleoyl Ethyl Amide Counteracts Bladder Overactivity in Female Rats Giorgio Gandaglia, 1,2 * Frank Strittmatter, 2,3 Giovanni La Croce, 1,2 Fabio Benigni, 1 Arianna Bettiga, 1 Fabio Castiglione, 1,2 Marco Moschini, 1 Francesco Mistretta, 1 Christian Gratzke, 3 Francesco Montorsi, 1 Christian Stief, 3 and Petter Hedlund 1,4 1 Urological Research Institute, San Raffaele Scientific Institute, Milan, Italy 2 Department of Clinical and Experimental Pharmacology, Lund University, Lund, Sweden 3 Department of Urology, Munich University, Munich, Germany 4 Department of Clinical Pharmacology, Link € oping University, Link € oping, Sweden Aims: To study micturition and bladder overactivity in female rats after chronic treatment with the fatty acid amide hydrolase (FAAH) inhibitor oleoyl ethyl amide (OEtA). Methods: Sprague–Dawley rats received daily subcutaneous injections of OEtA (0.3 mg/kg), or vehicle for 2 weeks. Cystometries, organ bath studies, Western blot, and immunofluorescence were then used. Expressions of FAAH, cannabinoid 1 and 2 receptors (CB1 and CB2), mitogen- activated protein kinase (MAPK), vesicular acetyl choline-transporter protein (VAChT), and calcitonin gene-related peptide (CGRP) were evaluated. Results: At baseline, OEtA-treated rats had higher values (P < 0.05) of micturition intervals (MI) and volumes (MV), bladder capacity (BC), threshold pressure, and flow pressure than vehicle controls. Intravesical PGE 2 reduced MI, MV, and BC, and increased basal pressure and the area under the curve in all rats. However, these urodynamic parameters were altered less by intravesical PGE 2 in OEtA-treated rats (P < 0.05 vs. vehicle controls). Compared to vehicle controls, detrusor from OEtA-treated rats had larger contractions to carbachol at 10–0.1 mM, but no difference in E max was recorded. FAAH, CB1, CB2, VAChT, or CGRP was similarly expressed in bladders from all rats. In separate experiments, intravesical OEtA increased mucosal expression of phosphorylated MAPK. Conclusions: Chronic FAAH inhibition altered sensory urodynamic parameters and reduced bladder overactivity. Even if it cannot be excluded that OEtA may act on central nervous sensory pathways to contribute to these effects, the presence of FAAH and CB receptors in the bladder and activation of intracellular signals for CB receptors by intravesical OEtA suggest a local role for FAAH in micturition control. Neurourol. Urodynam. 33:1251–1258, 2014. # 2013 Wiley Periodicals, Inc. Key words: cannabinoid receptor; endocannabinoid system; mitogen-activated protein kinase; urinary bladder INTRODUCTION Overactive bladder (OAB) is a common condition with a negative impact on patient health related quality of life. A recent report on low levels of adherence to therapy with antimuscarinics questioned the balance between the efficacy and tolerability of these agents, suggesting the exploration of new therapeutic options for OAB. 1 Findings that cannabis extracts or D9-tetrahydrocannabinol (THC) reduced urge incontinence episodes, urgency, frequency, and nocturia in patients affected by multiple sclerosis (MS) have brought attention to cannabinoid-mediated signals in lower urinary tract (LUT) functions. 2,3 Cannabinoid (CB) receptors have been shown to be expressed in the bladder, 4–6 and a peripheral modulatory function by CB-receptors on sensory neuronal activity has been proposed. 4,7 In support of a role for CB in afferent functions of micturition, other inves- tigations reported effects by CB agonists on urodynamic parameters considered to reflect sensory signals during micturition. 8,9 Also, in a recent investigation of a mixed population of patients with multiple sclerosis (MS) or OAB, treatment with Sativex  R , a novel drug that contains THC and cannabidiol, had favorable effects on frequency, urgency, or nocturia. 10 Still, the mechanism of action for CB on LUT symptoms (LUTS) has not been defined, and possible sites of action also include the central nervous system (CNS). 9,10 As such, the use of exogenous CB agonists as a therapeutic option for OAB may be limited by risk of CNS adverse effects. Novel findings suggest a role for the endocannabinoid- regulator enzyme fatty acid amide hydrolase (FAAH) in micturition function. 6,11 The FAAH, a key enzyme for the degradation of the endocannabinoid anandamide (AEA) and other fatty acid amides (FAAs), 12,13 was shown to be expressed in mouse, rat, and human urinary bladders. 6 Acute administra- tion of Oleoyl Ethyl Amide (OEtA), a FAAH inhibitor, was reported to affect sensory urodynamic parameters during micturition in rats. 6,11 Peripheral and central FAAH signals may be dissociated, and cannabis-like adverse behaviors are not encountered in FAAH knockout mice or after its inhibition. 14,15 Hence, targeting the homeostasis of endocannabinoids may by- pass risks for undesirable adverse events by exogenous CB that are caused by saturation of CB-receptors. 6,16 In this context, no study investigated the effects of chronic FAAH inhibition on bladder overactivity (BO). The aim of this Giorgio Gandaglia and Frank Strittmatter contributed equally to the manuscript. Christopher Chapple led the peer-review process as the Associate Editor responsible for the paper. Conflict of interest: none.  Correspondence to: Giorgio Gandaglia, M.D., Urological Research Institute, University Vita-Salute San Raffaele, Via Olgettina 60, 20132 Milan, Italy. E-mail: giorgan10@libero.it, giorgio.gandaglia@gmail.com Received 15 May 2013; Accepted 19 July 2013 Published online 29 August 2013 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/nau.22482 # 2013 Wiley Periodicals, Inc.